Masticatory Muscle Myositis

Overview

Masticatory muscle myositis (MMM) is an inflammatory condition involving the muscles of mastication or chewing in the dog. MMM is caused by an immune mediated process targeted against specific muscle fibers.

MMM occurs in all breeds of dog, but appears to be more common in German shepherds, Doberman pinschers and retrievers. Young and middle-aged dogs are most commonly affected. MMM has not been reported in the cat.

The disease occurs in both acute and chronic forms, and the signs may vary with each form. The chronic form is seen more commonly.

Diagnosis and Treatment Notes:

  • Masticatory muscle myositis is generally diagnosed by history and physical examination findings. Bloodwork, muscle biopsy, electromyography and skull x-ray can help rule out other diseases.
  • Treatment depends on the severity of the disease, your individual pet, and your veterinarian. The majority of dogs with masticatory muscle myostitis are treated with high doses of corticosteroids and/or other immunosuppressive drugs. Some may require a feeding tube during treatment. Discuss treatment details when your pet is diagnosed with this condition.

What to Watch for*:

  • Swelling associated with facial and forehead muscles
  • Fever
  • Pain upon opening the mouth
  • Reluctance to eat or chew
  • Excessive salivation
  • Shrinkage of head muscles
  • Inability to open the mouth normally 

*Please notify us if you notice any of the above signs or if you have any questions!